Device for tightly fastening at least two members

ABSTRACT

The invention relates to a device for clamping at least two components  17, 18 , in particular components  17, 18  for aircraft, in order to join the components  17, 18  by means of a weld seam  22  formed between two component edges  20, 21  via friction stir welding, wherein the components  17, 18  each are accommodated by several supporting elements  6 - 16 , and a welding backup plate  3  is arranged under the weld seam  22.    
     According to the invention, both sides of the welding backup plate  3  each have at least one mounting device  4, 5  that can be exposed to a vacuum for securing the components  17, 18.    
     The mounting devices  4, 5  that can be placed under a vacuum enable the rapid and easy clamping of components  17, 18  for purposes of joining via the known friction stir welding process. Because fewer parts are exchanged, in particular the mounting devices  4, 5  and/or the welding backup plate  3 , the device according to the invention can be easily and flexibly adapted to a plurality of components  17, 18  with varying component geometries and/or component dimensions. The very same device can be used to clamp a plurality of component types, in particular components  17, 18  with single or double curves for the friction stir welding process. Use of the device is here not limited to raw components, e.g., blanks or the like. Rather, complex, prefabricated single components, e.g., entire fuselage shells or partial shells, can be clamped and welded.  
     In addition, the device according to the invention also enables higher rates of advance during friction stir welding, because heat dissipation from the weld formation area  19  can be minimized via the use of poorly heat-conductive materials for the mounting devices  4, 5  and/or the substructure  2.

RELATED APPLICATION

This application claims the priority of German Patent Application DE 102004 062 997.8, submitted on Dec. 22, 2004, which hereby is incorporatedinto this application by reference.

This application claims the priority of German Patent Application DE 102004 062 997.8, submitted on Dec. 22, 2004, which hereby is incorporatedinto this application by reference.

FIELD OF THE INVENTION

The invention relates to a device for clamping at least two components,in particular components for aircraft, in order to join the componentsby means of a weld seam formed between two component edges via frictionstir welding, wherein the components each are accommodated by severalsupporting elements, and a welding backup plate is arranged under theweld seam.

BACKGROUND OF THE INVENTION

Known devices for clamping components for friction stir welding consistof a massive, as a rule flat substructure, on which the components to bewelded rest. Massive tension jacks mechanically clamp the componentsduring the welding process. The tension jacks must be laid in a ratherstable manner owing to the high mechanical forces that arise duringfriction stir welding. For example, such tension jacks can be realizedby means of bolted gripping jaws or hydraulically actuated grippingjaws.

Both cases are associated with a high initial outlay. In addition, themechanical tension jacks limit the dimensions for the components to bemachined, since the tension jacks must be brought as close to the weldformation area as possible in order to hold the components down on awelding backup plate as effectively as possible in this area. Very largeand complex components, e.g., fuselage shells in aircraft construction,can hence not be joined via friction stir welding using the knowndevices for clamping components.

Further, clamping the components to be joined via friction stir weldingis a rather time-consuming endeavor.

In addition, the massive configuration of known devices for clampingcomponents for friction stir welding necessitates a high level of heatdissipation from the weld formation area, so that the rate of advancemust be reduced in many cases.

Finally, these previously known devices do not enable simple and easyadjustment to different component geometries, in particular differentcomponents with single and double curves. Rather, a special device mustbe provided for each existing component geometry for clamping purposes,which significantly increases the storage outlay and costs.

Also known are flat vacuum clamping tables, which reduce the time neededfor clamping the components to be machined. However, these vacuumclamping tables also have a very massive structure, once again posingthe problem of an elevated heat removal from the weld formation area.

Further, the flat vacuum clamping tables are not easily adapted tovarious component geometries.

In light of the above disadvantages, the previously known embodiments ofdevices for clamping components for purposes of friction stir weldingare only conditionally suitable for the cost-effective and efficientincorporation into contemporary, highly flexible production processes.

SUMMARY OF THE INVENTION

In an exemplary embodiment of the invention, the disadvantages of theknown configurations of devices for clamping components for purposes offriction stir welding can be largely avoided.

One exemplary embodiment of the invention provides for a device with thefeatures set forth in claim 1.

The fact that both sides of the welding backup plate each have at leastone mounting device that can be exposed to a vacuum for securing thecomponents makes it possible to apply a vacuum to easily and rigidlyclamp together the components to be butt-jointed via friction stirwelding. In addition, the device according to the invention can enablethe variable clamping of various components with single or double curvesusing one and the same device, wherein only the mounting devices and/orwelding backup plate must essentially be tailored to the variouscomponent geometries.

In another advantageous embodiment of the device according to theinvention, the mounting devices are detachably secured on asubstructure. For example, this enables a rapid and simple exchange ofready mounting devices for various component geometries and/or componentdimensions. In addition, the substructure can establish a stable,load-bearing connection to a base plate, on which the entire deviceaccording to the invention rests.

In another advantageous embodiment, a surface geometry of the mountingdevices is tailored to a component surface geometry and/or componentdimensions.

This embodiment enables the reliable clamping of components withdifferent geometries and/or varying dimensions. In particular, thedevice according to the invention makes it easy to reliably fixcomponents with single and/or double curves in place for purposes offriction stir welding, wherein only the mounting devices and potentiallythe welding backup plate need to be exchanged.

In another advantageous embodiment of the device, one width of themounting devices is especially tailored to different materialthicknesses of the components.

This embodiment ensures that the device can be flexibly tailored to aplurality of various components, in particular to components withdifferent material thickness. In this case, the width of the mountingdevices increases as does the material thickness of the components to bewelded, so as to achieve a sufficient contact pressure during thefriction stir welding process. This is because the forces encounteredduring friction stir welding increase as material thickness grows. Inaddition, the mounting devices are each individually tailored tocomponents with a single and/or double curve as needed.

In another advantageous embodiment, the welding backup plate isessentially arranged centrally below the weld seam in a weld formationarea, and is replaceably designed.

This enables an easy exchange of the backup plate, which is susceptibleto wear. In addition, the components to be welded can be supported in anessentially symmetrical manner, which can help to improve the weld seamquality. Further, a fine adjustment to the geometric shape of thecomponents in the weld formation area can be achieved if needed, e.g.,by using different backup plates for various component geometries. Thewelding backup plate can be made out of a metallic material to ensure asufficient service life or wear resistance during friction stir weldingoperations.

In another advantageous embodiment, the welding backup plate andmounting devices form a support surface. This ensures that thecomponents to be connected via friction stir welding come to lie asflush as possible against the device according to the invention, therebyyielding a good height and dimensional stability of the weld seam formedvia friction stir welding. The welding backup plate and mounting deviceshere form an imaginary, essentially continuous support surface.

In another embodiment of the device according to the invention, thecomponents in the weld formation area can be pressed against the weldingbackup plate by at least one contact element, in particular, a pressureroller. This can further improve positioning of the components in theweld formation area during friction stir welding.

In another advantageous embodiment, the support elements are movable forpurposes of adjustment to various surface geometries and/or dimensionsof the components.

As a result, components with varying geometries and/or dimensions can beflexibly accommodated. A plurality of support elements is herepreferably arranged on either side of the mounting devices, so that evenlarge components can be securely accommodated. The support elements arehere designed essentially for perpendicular movement. In addition, thesupport elements can also be positioned in the plane.

In another embodiment of the invention, the support elements haveconnecting elements, in particular suction cups, for fixing thecomponents in place. This embodiment enables a reliable grip even incases of large components, e.g., fuselage shells. Connecting elementsother than suction cups can also be used, e.g., clamps or the like.

In another advantageous embodiment, the mounting devices and/or thesubstructure are provided with a heat-insulating material. This ensuresthat the heat that arises during the friction stir welding process inthe weld formation area or weld seam only dissipates slightly into thedevice, thereby enabling an increase in the rate of advance of thefriction stir welding tool.

In another advantageous embodiment of the invention, at least onepositioning unit is arranged in the area of the mounting devices and/orthe substructure in order to advance and/or align the componentsrelative to the welding backup plate and/or mounting devices.

This embodiment enables an at least semiautomatic positioning of thecomponents to be welded on the device. The positioning units can bedesigned as articulated brackets with suction cups at their ends. Thearticulate brackets can be enabled using actuators, for example, inparticular hydraulic pistons, electric drives or the like. In addition,the articulated brackets can also be fitted with sensors for acquiringtheir spatial position or the spatial position of the components. Thearticulated brackets are controlled with a suitable open and closed-loopcontrol system. The open and closed-loop control system makes itpossible to simultaneously control the friction stir welding tool andmounting devices.

The drawing shows:

FIG. 1 A perspective view of the device according to the invention forclamping components during the friction stir welding of components alongcomponent edges.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an exemplary embodiment of the deviceaccording to the invention for clamping two components to be joinedtogether via friction stir welding.

Among other things, the device according to the invention comprises abase plate 1, a substructure 2, a welding backup plate 3 and themounting devices 4, 5. The support elements are preferably each arrangedlike a matrix, each spaced uniformly apart from the other. In thedepiction on FIG. 1, only the support elements 6 to 16 have been shownto gain a clearer graphical overview.

A first component 17 and second component 18 rest on the mountingdevices 4, 5 as well as support elements 6 to 16. The components 17, 18can consist of sheets or more complex components, e.g., segments offuselage shells or the like.

The components 17, 18 are connected in a weld forming area 19 along thecomponent edges 20, 21 via the weld seam 22. The weld seam 22 is formedin a known manner via friction stir welding using a suitable frictionstir welding tool 23, which is situated on a tool carrier 24. Forexample, the tool carrier 24 is guided by a computer-controlled portalrobot (not shown in any greater detail) in the direction of the arrow 25along the component edges 20, 21 to create the weld seam 22.

Since considerable mechanical forces arise during friction stir welding,the components 17, 18 must be securely fixed or clamped by means of thedevice according to the invention. The weld formation area 19 liesloosely on the welding backup plate 3. The upper sides of the mountingdevices 4, 5 facing the components 17, 18 have a plurality of channels(not shown in any greater detail), which can be placed under a vacuum.

For example, the channels can be milled into the upper sides of themounting devices 4, 5 in a checkerboard pattern, or incorporated in someother way. As an alternative, a matrix of boreholes can be incorporatedinto the upper sides of the mounting devices 4, 5 to be able toestablish a vacuum between the components 17, 18 and the mountingdevices 4, 5.

Also situated on the edge areas of the mounting devices 4, 5 are sealingstrips in order to maintain the vacuum between the components 17, 18 andthe mounting devices 4, 5. As a result of the vacuum between thecomponents 17, 18 and the mounting devices 4, 5, the ambient airpressure exposes the components 17, 18 to a high contact pressure. Giventhe generally large components 17, 18, relatively high contact forcescan hence be generated, so that the components 17, 18 do not shift, evenat high rates of advance for the friction stir welding tool 23.

The mounting devices 4, 5 are detachably connected with the substructure2, e.g., by means of screws, clamps, latches or the like, so as toensure an easy exchange of the mounting devices 4, 5 as a function ofthe geometry and/or the dimensions of the components 17, 18 to beclamped in place. In addition, the substructure can be detachablysecured to the base plate 1 in order to achieve a higher flexibilitywith respect to varying components.

To buttress the action of the mounting devices 4, 5, in particular inthe case of large components 17, 18, the device also has the supportelements 6 to 16. The support elements 6 to 16 can each be movedindependently from each other in the direction of the black doublearrows, i.e., in the z-direction. This makes it possible to alsoreliably and securely clamp components with varying dimensions and/orgeometry using the device according to the invention. In addition, thesupport elements 6 to 16 can also be designed to move in the x andy-direction.

The welding backup plate 3 and upper sides of the mounting devices 4, 5form a roughly continuous support surface 26, on which the components17, 18 rest on either side of the component edges 20, 21. This fictivesupport surface 26 continues to both sides in the form of the supportelements 6 to 16 arranged like a matrix.

To improve the support action of all support elements 6 to 16, thelatter have terminal connecting elements, e.g., in the form of suctioncups 27 to 30. In this case, all support elements 6 to 16 along with theother support elements (not shown) are fitted with suction cups, whereinthe suction cups 27 to 30 are penciled in on FIG. 1 to represent thesuction cups that cannot be shown. It should be noted in thisconjunction that the support elements do not absolutely have to befitted with suction cups to achieve a sufficient clamping action for thedevice. The contact forces generated via the mounting devices 4, 5 asthe result of a vacuum are generally sufficient to achieve reliablefixation during the friction stir welding process.

To further improve the clamping effect of the mounting devices, 4, 5,the tool carrier 24 can have a pressure roller 31. The pressure roller31 tightly presses the component edges 20, 21 against the welding backupplate 3 once again just prior to the friction stir welding tool 23 weldsthe components 17, 18 in the weld formation area 19. The pressure roller31 is also not absolutely necessary for achieving a sufficient contactforce in the area of the component edges 20, 21 in the weld formationarea 19.

The measures described above for clamping the components 17, 18 preventthe components 17, 18 from slipping during the friction stir weldingprocess, so that the components 17, 18 can be connected at maximumdimensional stability via friction stir welding.

The greater the material thickness of the components 17, 18, the greatera width 32, 33 must be selected for the mounting devices 4, 5 in orderto achieve sufficiently high contact forces by generating the vacuum.

When clamping components 17, 18 with a geometric shape differing fromthe one shown on FIG. 1 by means of the device according to theinvention, it is necessary to at least change out the mounting devices4, 5, replacing them with mounting devices suitably tailored to thegeometric shape of the components. Correctly designing the upper sidesof the respective ready mounting devices and their widths makes itpossible to tailor the device according to the invention to a pluralityof different components with varying geometric dimensions with minimaloutlay. In particular, it is also possible to reliably and securelyclamp complex, simple and/or double-curved components just by changingout correspondingly designed mounting devices. In addition, it may benecessary to provide special substructures and special backup plates forpurposes of adjustment to component geometries and/or dimensions.Fixation then takes place in the outside area of the components by meansof the so-called “support element field” that can be adapted to aplurality of varying component geometries and/or dimensions and consistsof a plurality of support elements arranged as a matrix.

However, according to the invention it is no longer necessary to providea complete, individual clamping device for each component geometryencountered in the production process, which yields a significant costand time savings.

Also situated on either side of the substructure 2 are positioning units34, 35, which enable a fine positioning of the applied components 17, 18relative to the welding backup plate 3. In this case, the drawing onFIG. 1 shows only two positioning units 34, 35. Other positioning unitsare arranged on either side of the substructure 2, preferably eachspaced uniformly apart, to achieve a more efficient positioning of thecomponents 17, 18 along the x-direction. The positioning units 34, 35each have connecting elements, e.g., suction cups 36, 37, for repeateddetachable connection to the components 17, 18. The suction cups 36, 37are again representative for the other connecting elements on thepositioning units (not shown in any greater detail).

The substructure 2, base plate 1 and mounting devices 4, 5 are formedwith a metallic material, e.g., with an aluminium alloy, with steel orthe like. As opposed to the described material selection, at least themounting devices 4, 5 can also be made out of an only slightly thermallyconductive material, e.g., a suitable ceramic and/or plastic. Thisdiminishes the heat dissipation from the weld formation area 19, therebyenabling higher rates of advance at the same quality of weld seam withthe friction stir welding tool 23.

Further, the components 17, 18 exhibit small outlet areas 38, 39 in theweld formation area 19, which are separated out upon conclusion of thefriction stir welding process. As shown by example in the drawing onFIG. 1, the outlet areas are designed as small, strap-likecontinuations. As a result, the weld seam 22 always runs all the way upto a front or rear component edge of the components 17, 18. By contrast,if the friction stir welding tool 23 were only to extent up to the frontor rear component edge, the weld seam 22 would be only incompletelyformed in these edge areas.

In addition, it must be noted that “comprising” does not preclude anyother elements or steps, and “one” or “a” does not preclude a plurality.Further, it should be noted that features or steps that were describedwith reference to one of the above exemplary embodiments can also beused in combination with other features or steps from other exemplaryembodiments described above. Reference numbers in the claims are not tobe regarded as limiting.

REFERENCE LIST

-   1 Base plate-   2 Substructure-   3 Welding backup plate-   4 Mounting device-   5 Mounting device-   6 Support element-   7 Support element-   8 Support element-   9 Support element-   10 Support element-   11 Support element-   12 Support element-   13 Support element-   14 Support element-   15 Support element-   16 Support element-   17 First component-   18 Second component-   19 Weld formation area-   20 Component edge-   21 Component edge-   22 Weld seam-   23 Friction stir welding tool-   24 Tool carrier-   25 Arrow-   26 Support surface-   27 Suction cup-   28 Suction cup-   29 Suction cup-   30 Suction cup-   31 Pressure roller-   32 Width-   33 Width-   34 Positioning unit-   35 Positioning unit-   36 Suction cup-   37 Suction cup-   38 Outlet area-   39 Outlet area

1. A device for clamping at least two components (17, 18), in particularcomponents (17, 18) for aircraft, in order to join the components (17,18) by means of a weld seam (22) formed between two component edges (20.21) via friction stir welding, the device comprising: several supportingelements (6-16); a welding backup plate (3); wherein the components (17,18) each are accommodated by several supporting elements (6-16), and thewelding backup plate (3) is arranged under the weld seam (22), whereinboth sides of the welding backup plate (3) each have at least onemounting device (4, 5) with a plurality of channels, which can be placedunder a vacuum for clamping the components (17, 18).
 2. The deviceaccording to claim 1, wherein the mounting devices (4, 5) are detachablysecured to a substructure (2).
 3. The device according to claim 1,wherein a surface geometry of the mounting devices (4, 5) is tailored toa surface geometry of the components (17, 18) and/or to dimensions ofthe components (17, 18).
 4. The device according to claim 1, wherein onewidth (32, 33) of the mounting devices (4, 5) is especially tailored tovarying material thicknesses of the components (17, 18).
 5. The deviceaccording to claim 1, wherein the welding backup plate (3) isessentially arranged centrally below the weld seam (22) in a weldformation area (19), and replaceably designed.
 6. The device accordingto claim 1, wherein the welding backup plate (3) and the mountingdevices (4, 5) form a support surface (26).
 7. The device according toclaim 1, wherein the components (17, 18) in the weld formation area (19)can be pressed against the welding backup plate (3) by at least onecontact element, in particular, a pressure roller (31).
 8. The deviceaccording to claim 1, wherein the support elements (6-16) are movablefor purposes of adjustment to various surface geometries and/ordimensions of the components (17, 18).
 9. The device according to claim1, wherein the support elements (6-16) have connecting elements, inparticular suction cups (27-30), for fixing the components (17, 18) inplace.
 10. The device according to claim 1, wherein the mounting devices(4, 5) and/or the substructure (2) are provided with a heat-insulatingmaterial.
 11. The device according to claim 1, wherein at least onepositioning unit (34, 35) is arranged in the area of the mountingdevices (4, 5) and/or the substructure (2) in order to advance and/oralign the components (17, 18) relative to the welding backup plate (3)and/or mounting devices (4, 5).